A window portion is premade on the back of the computer chassis to correspond to a connection port assembly on the motherboard, so that the connection port assembly is exposed via the window portion. The connection port assembly includes several connection ports, and the gaps between the connection ports have to be covered. As a result, an additional shielding plate corresponding to the connection port assembly is assembled on the window portion. The shielding plate covers the gaps between the connection ports, and the connection ports are via corresponding openings on the shielding plate. The shielding plate is a detachable structure. For different connection port assembly, different shielding plates are assembled onto the computer chassis.